This invention relates to an apparatus for passing a working medium through a continuously moving permeable fabric web, comprising a slot nozzle extending over the entire working width of the apparatus and at least one cover element arranged on that side of the fabric web remote from the slot nozzle.
It frequently happens, particularly in the treatment of textile webs, that a working medium has to be passed through the textile web under pressure or suction. A typical example of this is the removal of water from wet-treated textile webs where the textile web is transported for example over the narrow opening of a slot nozzle which is connected to a suction fan so that liquid is withdrawn from the textile web as it passes over the slot nozzle opening. It is also possible to pass a working medium for example through a permeable plastics web.
In addition, it is known that either a gaseous medium (for example air) or a liquid medium (for example water or the like) can be passed through a web of this type.
Since an apparatus of the type in question and the slot nozzle which it contains are generally designed for fabric webs of different widths, it frequently happens that the width of the fabric web being treated is narrower than the working width of the apparatus and the effective width of the slot nozzle. For this reason, it is necessary to associate with the slot nozzle a cover element by which those parts of the slot nozzle opening which remain exposed adjacent the edges of the fabric web can be covered so that no extraneous air is led past the edges of the fabric web to be treated.
Various types of cover elements for the slot nozzle opening are known in practice. In one known embodiment, the cover element consists essentially of a kind of rubber lip which is applied to the exposed part of the slot nozzle opening. In another known embodiment, the cover element consists of a flexible tube which is held over the central portion of the working width of the slot nozzle in such a way that it hangs down at both ends. In the case of a suction-type slot nozzle, the reduced pressure sucks the flexible tube into the side regions of the slot nozzle opening which are not covered by the fabric web to be treated, so that the full reduced pressure is always automatically directed onto the fabric web.
With all these known embodiments, it has been found that the working medium is generally not passed through with sufficient intensity. In other words, the fabric web to be treated is not adequately permeated by the working medium.